Wholesale prices leapt to a record $283 per megawatt hour last month and are the highest in the nation.

Spot prices have also surged to $15,100/MWh eight times in Queensland in the last 12 months.

Generators were again selling electricity at that price on Sunday when the market operator capped prices at $300/MWh, triggering the current supply crisis.

Queensland Energy Minister Mick de Brenni says high international fossil fuel prices, winter demand and outages at public power plants have been driving up wholesale prices.

But the Australian Energy Regulator has indicated a fourth factor may be at play.

AER chair Clare Savage this week warned generators against price gouging in wholesale markets.

“Market participants must not make a dispatch offer, dispatch bid or rebid that is false or misleading,” she wrote in a letter to generators on Tuesday.

“An offer/bid or rebid is taken to be false or misleading if the party … does not have a reasonable basis for making the offer.”

The state’s 17 coal and gas-fired plants are run by public-owned Stanwell Corporation, CS Energy and CleanCo, and private generators Arrow Energy, Alinta Energy, Intergen, Origin Energy, QGC and RATCH Australia.

All of those power stations either own coal mines or gas fields, or are on long-term fuel supply contracts, so they don’t pay international prices for coal and gas.

Mr de Brenni denies public generators have been price-gouging, saying they only offer prices to “cover costs”.

However, AER reports show Stanwell, CS and CleanCo have all offered electricity to the grid for up to $15,100/MWh during the last 12 months.

Victoria University’s Professor Bruce Mountain, an energy economist and director of the Victoria Energy Policy Centre, says there should be an inquiry into Queensland’s wholesale prices.

He says a parliamentary inquiry or the Crime and Corruption Commission need to look at generators’ books.

“We need a frank and fearless, open inquiry into what’s going on,” he told AAP on Wednesday.

“Things have gotten to the point where the breakdown is so complete, and so severe, that the generators’ confidentiality concerns need to be weighed against the public interest.”

Liberal National Party energy spokesman Pat Weir accused the Labor government of milking the generators for profits.

“The government should be transparent about how they are using generators and how they will deliver affordable, clean and reliable electricity,” he told AAP.

Katter’s Australian Party and the Greens backed a probe into wholesale price gouging, but both crossbench parties also blame a lack of government planning for the crisis.

Greens MP Michael Berkman said more energy storage is needed, while KAP leader Robbie Katter said the state needs a gas reserve.

Prof Mountain said governments should want to know how their policies are affecting electricity prices.

“How have we ended up in the situation? How have the generators behaved? What are the costs? What is their exposure to coal and gas, spot markets and so on?” he told AAP.

“And that’s entirely in the minister’s remit, as well as the CCC and other entities.”